Dual Center Speakers

[walter duque]

I was just playing around and put another center speaker on top of my TV and I have to say it sounds great. Any pros and cons on this type of set up.

 

[jostenmeat]

Phase and/or comb-filtering issues up the yin yang.

 

[walter duque]

Phase and/or comb-filtering issues up the yin yang.

Thanks, good to know. But sounds great.

 

[jostenmeat]

Thanks, good to know. But sounds great.

That's all that matters I suppose. You're welcome.

 

[MinusTheBear]

Pro:
For improved coverage or use with a large screen and a front projector, try two center channel speakers, one above and one below the screen. That way, for most viewers, the two centers running in parallel will image the dialog in the center of the screen, rather than too far above or below the screen. This dual center-channel formation will also reduce the effect of the location on the tonal balance....taken from link below.

http://www.axiomaudio.com/tips_center_channel_sound.html

 

[Bugbitten]

I was just playing around and put another center speaker on top of my TV and I have to say it sounds great. Any pros and cons on this type of set up.

Been doing this for 4 years with no phase and/or comb-filtering issues.

 

[jostenmeat]

Been doing this for 4 years with no phase and/or comb-filtering issues.

I absolutely refuse to believe you.

 

[walter duque]

Pro:
For improved coverage or use with a large screen and a front projector, try two center channel speakers, one above and one below the screen. That way, for most viewers, the two centers running in parallel will image the dialog in the center of the screen, rather than too far above or below the screen. This dual center-channel formation will also reduce the effect of the location on the tonal balance....taken from link below.

http://www.axiomaudio.com/tips_center_channel_sound.html

I am using a Pionner 1140 50" Plasma in this room. The bottom center front has a 11 degree angle it can be used for top or bottom center. I am using this for my bottom and one of my rear surrounds which is a WTW design (Coherent Pulse) for top center, both have dual 6" drivers except the bottom center has 3 tweeters where the top only has one.

 

[Bugbitten]

I absolutely refuse to believe you.

That's fine.

 

[the grunt]

I’ve tried many different combinations of center speakers and also thought that two centers sounded better than one. However, I hadn’t calibrated the SPL to be equal when I added the second one. After recalibrating I found that most of what sounded better was that it was louder.

Also I initially liked the “wall of sound” I could create by how far I separated them but with more listening I found that while I liked this effect for movies it tended to smear the front soundstage for music.

As for phase and comb-filtering they were very noticeable in all dual center configurations with pink noise from the calibration disk. However, with music and movies it was only noticeable when the drivers were separated by certain distances from each other relative to the distance to the listening position. In one configuration there was a peak and a null on opposite sides of my head and it sounded like wearing headphones with only one side playing, very uncomfortable.

Personally, I found that it sounded good with movies (very movie-theater-like) and could see some cases where it would be beneficial (large rooms, sitting close to a big screen). However, for music it was a total no-go for me except for some live concert CD/DVDs where discrete instrument/vocalist placement wasn’t there in the first place.

In the end if you like it then it’s good.

 

[walter duque]

I’ve tried many different combinations of center speakers and also thought that two centers sounded better than one. However, I hadn’t calibrated the SPL to be equal when I added the second one. After recalibrating I found that most of what sounded better was that it was louder.

Also I initially liked the “wall of sound” I could create by how far I separated them but with more listening I found that while I liked this effect for movies it tended to smear the front soundstage for music.

As for phase and comb-filtering they were very noticeable in all dual center configurations with pink noise from the calibration disk. However, with music and movies it was only noticeable when the drivers were separated by certain distances from each other relative to the distance to the listening position. In one configuration there was a peak and a null on opposite sides of my head and it sounded like wearing headphones with only one side playing, very uncomfortable.

Personally, I found that it sounded good with movies (very movie-theater-like) and could see some cases where it would be beneficial (large rooms, sitting close to a big screen). However, for music it was a total no-go for me except for some live concert CD/DVDs where discrete instrument/vocalist placement wasn’t there in the first place.

In the end if you like it then it’s good.

I have to agree with you, great for movies not for music, unless you turn both centers down low.

 

[Exit]

I believe there are issues with serial and parallel hook up of two speakers off of one amplifer channel. Audioholics did a thread or post on this but I was unable to locate it. I think their bottom line was to stick to one speaker.

 

[fmw]

Using two speakers does two things. It increases the volume and increases the bass response by causing more air move. You should be able to accomplish the same thing with volume level and EQ adjustments.

 

[walter duque]

I believe there are issues with serial and parallel hook up of two speakers off of one amplifer channel. Audioholics did a thread or post on this but I was unable to locate it. I think their bottom line was to stick to one speaker.

I do use 2 seperate channels for the centers, I am using a Cinepro 3k6 with six channels. also a 1k2 for my 7.2 setup. It was just something I was curios about. I did put the system back to normal. I have the center channel bi-amped again.

 

[AcuDefTechGuy]

I believe there are issues with serial and parallel hook up of two speakers off of one amplifer channel. Audioholics did a thread or post on this but I was unable to locate it. I think their bottom line was to stick to one speaker.

Yeah, I believe it's called Comb Filtering, which causes some frequencies to add up and some to cancel out completely.

 

[walter duque]

Yeah, I believe it's called Comb Filtering, which causes some frequencies to add up and some to cancel out completely.

Like I said I did use two different channels.

 

[AcuDefTechGuy]

Like I said I did use two different channels.

We are talking about two Front Center speakers, right?

It has nothing to do with using two separate amplifiers and two dfferent channels.

It's about using two center speakers. Each center speaker is producing the same exact signal even though two separate amps are being used.

 

[Bugbitten]

combing effects of dual center channels

From Axiom's Alan Lofft:

While combing effects are easily heard using a pink-noise test signal (and are measureable), they are not significant or audible with music or soundtrack playback.

Moreoever, any speaker or two speakers produce comb-filtering effects. Try it with one speaker and pink noise. As you move your head slightly to one side or the other--only a few inches are necessary-- the arrival times of sounds to each of your ears change as your head changes position and the distance from the speaker driver to each ear changes, resulting in audible comb-filtering effects. You'll hear the high-frequency content alternately increase and decrease because of cancellation and reinforcement.

The notion of time-coherency when put to the test under controlled listening conditions is a lot of high-end blather not based on scientifically controlled listening tests.

It simply doesn't matter with music or soundtrack playback. If we were all ultra-sensitive to combing effects with musical playback from loudspeakers, we'd all be complaining. It would be intolerable.

Regards,
_________________________
Alan Lofft,
Axiom Resident Expert

Axiom Forum Discussion thread

 

[AcuDefTechGuy]

From Axiom's Alan Lofft:



Axiom Forum Discussion thread

Well, who are you going to believe?

A speaker company who wants you to buy more of their speakers?

Of course, you can try it out. But just make sure that you can return the speaker if you don't like the result. If it's free to try, then you have nothing to lose.

But just theoretically, what do you think you will gain with 2 center speakers?

Increased in dialogue volume? You could just simply increase the volume knob.

Increased in clarity of sound? I don't see how.

 

[avaserfi]

Our ears aren't microphones, in fact the mechanisms involved in this process have actually been shown to be so advanced that we will in a sense fill in the gaps. After all when "listening in the elaborate comb filters called concert halls" [1] it still sounds great. I believe Blauert says it best: "Clearly, then, the auditory system possesses the ability, in binaural hearing, to disregard certain linear distortions of the ear input signal in forming the timbre of the auditory event" [2].

As such adding a second center channel might not be so bad. As far as the gains? It would allow for a maximum of about 6dB more dynamics, but most likely 3 due to placement. It is very rare for typical home environments to need more than a single center channel. The argument for better soundstage is silly, just place your single center channel properly and it will be able to provide good soundstage for all listening unless you have an extremely large room. Rather, the benefits heard from the addition of a second center channel are likely due to the lack of level matching.

[1] Loudspeakers and Rooms for Sound Reproduction - A Scientific Review. Toole, Floyd E. J. Audio Eng. Soc., Vol. 54, No. 6, 2006 June.

[2] Spatial Hearing - The Psychophysics of Human Sound Localization, Blauert, J. rev. ed. MIT Press, Cambridge, MA, 1997.